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Topic: pack volume, for you math/physics geeks< Next Oldest | Next Newest >
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PostIcon Posted on: Feb. 06 2013, 12:30 pm  Skip to the next post in this topic. Ignore posts   QUOTE

Can anyone suggest an easy and accurate means by which to determine the volume of a pack.  I know the basic forumula for volume of course, (that's not rocket science) but with all the nooks, separate pockets, crannies, irregular contours, etc. of a pack, I don't think I can get an accurate measurement by simply measuring the dimensions and doing the math.

Thanks.


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PostIcon Posted on: Feb. 06 2013, 12:32 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE

Packing chips?

Or M&Ms. With or without the Almonds to aid in the packing efficiency.
http://tech.mit.edu/V124/N4/long_5.4w.html

Gotta love science.
"The researchers discovered that oblate spheroids, the shape of M&M's chocolate candies, pack surprisingly more densely than regular spheres when poured randomly and shaken. Extending the work with further experiments and sophisticated computer simulations, they found that a related shape, the ellipsoid, packs at random even more densely than the tightest possible, perfectly ordered arrangement of spheres. Previously, scientists did not know that randomly assembled particles could pack so densely."
http://www.princeton.edu/pr/news/04/q1/0212-candy.htm
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PostIcon Posted on: Feb. 06 2013, 12:35 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE


(High_Sierra_Fan @ Feb. 06 2013, 12:32 pm)
QUOTE
Packing chips?

Or M&Ms. With or without the Almonds to aid in the packing efficiency.
http://tech.mit.edu/V124/N4/long_5.4w.html

Jeeze, that's a  lot of M & Ms. :O

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PostIcon Posted on: Feb. 06 2013, 12:39 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE


(High_Sierra_Fan @ Feb. 06 2013, 9:32 am)
QUOTE
Packing chips?

Or M&Ms. With or without the Almonds to aid in the packing efficiency.
http://tech.mit.edu/V124/N4/long_5.4w.html

Gotta love science.
"The researchers discovered that oblate spheroids, the shape of M&M's chocolate candies, pack surprisingly more densely than regular spheres when poured randomly and shaken. Extending the work with further experiments and sophisticated computer simulations, they found that a related shape, the ellipsoid, packs at random even more densely than the tightest possible, perfectly ordered arrangement of spheres. Previously, scientists did not know that randomly assembled particles could pack so densely."
http://www.princeton.edu/pr/news/04/q1/0212-candy.htm

When wrestling with packing  a &*^$%##$%^&* bear canister I've sometimes wondered what the caloric load would be if I simply filled the thing with a thoughtful mix of M&Ms and SmokeHouse Almonds.

But then I recall a buddy of mine who tried such a thing (GORP only) on a route around North Lake South Lake and he did an alpine solo climb over a nasty col just to escape early from the horror of his diet....

Yeah those Staples or Office Depot biodegradable packing chips would be cheaper and lighter to boot.

As a Kurt Vennegut fan (Ice Nine in Cat's Cradle) I do like the M&M story.
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PostIcon Posted on: Feb. 06 2013, 12:53 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE

Rule #1:  Prolly stating common knowledge, but NEVER trust the volume spec (or most any spec) on the tag.  So, to find out volume for yourself...

Option 1:  Take manual measurements.  Too tedious?  Maybe spend more care with the main pocket -- and make more casual estimations with the smaller pockets?

Option 2:  Line the pockets with appropriately oversized plastic bags -- lawn bag for main, maybe gallon or quart plastic bags for other pockets.  One by one, starting with the main pocket, fill with water, then carefully tie.  When all completed, remove, untie and empty each into a sizable tub or bucket -- and measure the grand total volume.  As you know, the volume of outer pockets tend to decrease as the main one gets filled.  This method should help minimize the chance of overstating the total volume.  Still tedious, but playing with water can be fun.  :D


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PostIcon Posted on: Feb. 06 2013, 1:18 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE

Google it?

But do the pockets count? When measuring square feet of a house the basement(if not "finished") and holes in the crawl space won't count.
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PostIcon Posted on: Feb. 06 2013, 1:34 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE

Weigh the bag empty. Then fill it with as much water as it can hold and weigh it again. Calculate volume from water weight.

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PostIcon Posted on: Feb. 06 2013, 1:42 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE


(tomas @ Feb. 06 2013, 10:34 am)
QUOTE
Weigh the bag empty. Then fill it with as much water as it can hold and weigh it again. Calculate volume from water weight.

^^^THIS^^^

Rumi~the voluminous~Dude


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PostIcon Posted on: Feb. 06 2013, 1:47 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE

Thanks for the suggestions but:  first these are actually bicycle panniers and won't hold water if you guys are actually serious; second the panniers are so old, circa 1970s, that you can hardly google them.  I may have to buy some M & Ms.  I guess I can always save them for next Halloween. :)

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PostIcon Posted on: Feb. 06 2013, 2:01 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE

Use a garbage bag to line them and fill with water.  But if you go the M&Ms route, I like the new peanutbutter ones.

Rumi


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PostIcon Posted on: Feb. 06 2013, 2:05 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE

Yep... Hikerjer, you missed the part I wrote about lining the pack with bags first.  Given how a pack bulges... I think this is the best (most accurate) way to measure.

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PostIcon Posted on: Feb. 06 2013, 2:18 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE

Jer, of you go with the M&Ms I'll help you dispose of them :)

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PostIcon Posted on: Feb. 06 2013, 2:22 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE

I wonder to what extent the literal volume even matters. If you calculate the total volume of all the things you want to put in the pack, that still doesn't mean it will all fit -- for example, 40L of stuff almost certainly won't fit into a 40L pack because you can never fill every nook and cranny (just think about the space around a giant cylindrical bear can that doesn't get filled all the way). Ultimately what would seem to matter is whether all the stuff I want to take will fit in this pack or not, whatever the measurements say it holds.

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PostIcon Posted on: Feb. 06 2013, 2:25 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE

Good point, JR.  But I still want a share of the M&Ms.

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PostIcon Posted on: Feb. 06 2013, 2:30 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE

Fill it with anything solid.
Submerge it in water and measure the water dispersed.
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PostIcon Posted on: Feb. 06 2013, 3:02 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE


(RebeccaD @ Feb. 06 2013, 11:25 am)
QUOTE
Good point, JR.  But I still want a share of the M&Ms.

Dibbs on the SmokeHouse Almonds.
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PostIcon Posted on: Feb. 06 2013, 3:10 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE

Ya know, sometimes you guys are just plain weird.  ???  Not that ther's any thing wrong with that.

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PostIcon Posted on: Feb. 06 2013, 3:12 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE

Use packing peanuts.  Fill it and then empty them into a box.  Measure the size of the box and do the math.  One cubic ft equals 28.3 liters.  

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PostIcon Posted on: Feb. 06 2013, 3:14 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE


(hikerjer @ Feb. 06 2013, 12:10 pm)
QUOTE
Ya know, sometimes you guys are just plain weird.  ???  Not that ther's any thing wrong with that.

Hey we're not the ones angsting over a number that, when the rubber hits the road and it's time to just stuff all your gear into them* is just slightly less meaningful than the denier count of the fabric.

Just make sure they don't fall into an arrangement that freezes the world solid: I have some fun summer plans...

* TM just about every "what size pack" thread in the GEAR section.
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PostIcon Posted on: Feb. 06 2013, 3:15 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE

Fill it full of jello...

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PostIcon Posted on: Feb. 06 2013, 3:18 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE


(ol-zeke @ Feb. 06 2013, 12:12 pm)
QUOTE
Use packing peanuts.  Fill it and then empty them into a box.  Measure the size of the box and do the math.  One cubic ft equals 28.3 liters.  

I was thinking he could weigh them. Weigh a liter (first the bottle, then the bottle full of chips), weigh the empty pack, weigh the pack filled with the packing chips: subtract (we in the business call it the tare, if you have a scale that costs about five grand it'll do it for you): math it out and voila; the extra comfy mattress STILL won't fit!
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PostIcon Posted on: Feb. 06 2013, 3:39 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE


(hikerjer @ Feb. 06 2013, 3:10 pm)
QUOTE
Ya know, sometimes you guys are just plain weird.  ???  Not that ther's any thing wrong with that.

Hey, you asked for an accurate method and I gave you one. Not my fault that I flashed back to my astronomy undergraduate days and all the blasted lab classes I had to take. :;):

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PostIcon Posted on: Feb. 06 2013, 4:12 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE

get a couple garbage bags and put one inside the other.

Put the bags in your pack

Fill them full of water

Put a garbage pail on a scale and note the weight

Pour the water into the pail

A pint's a pound

Convert pints to cubic inches using one of those internet converter thingies
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PostIcon Posted on: Feb. 06 2013, 4:34 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE

Pack volume is really used to compare packs.  It is hard to fill every bit of the volume because that is just the nature of packing.  Somethings you pack will compress and mold around other objects and some things will not.  So if you are simply trying to compare the volume of your current set of panniers to a potential set or just wanting to know for whatever reason, use the water in a garbage bag method.  It really is rather simple and will give you a fairly accurate measurement.

Rumi


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PostIcon Posted on: Feb. 06 2013, 4:38 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE


(RumiDude @ Feb. 06 2013, 1:34 pm)
QUOTE
Pack volume is really used to compare packs.  It is hard to fill every bit of the volume because that is just the nature of packing.  Somethings you pack will compress and mold around other objects and some things will not.  So if you are simply trying to compare the volume of your current set of panniers to a potential set or just wanting to know for whatever reason, use the water in a garbage bag method.  It really is rather simple and will give you a fairly accurate measurement.

Rumi

Dude - stop copying me (post #5)!   :p

Ben <~~ the original world


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PostIcon Posted on: Feb. 06 2013, 5:08 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE


(RumiDude @ Feb. 06 2013, 4:34 pm)
QUOTE
e simply trying to compare the volume of your current set of panniers to a potential set, use the water in a garbage bag method.

You're a perceptive guy, Rumi.  That's exactly what I'm trying to do. I'll  give the garbage bag method a try.

Thanks all.  I think. ???


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PostIcon Posted on: Feb. 06 2013, 5:24 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE

Fill it full of hydrogen until it floats. Then see how many bricks you can tie on and it still floats. Have a gun ready to shoot it down in case it is in danger of floating away.
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PostIcon Posted on: Feb. 06 2013, 6:08 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE

Decibel meter?

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PostIcon Posted on: Feb. 06 2013, 6:17 pm Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE

take your empty pack to a highschool math class and have them calculate for a class project.
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PostIcon Posted on: Feb. 06 2013, 6:21 pm Skip to the previous post in this topic.  Ignore posts   QUOTE


(Marmotstew @ Feb. 06 2013, 3:24 pm)
QUOTE
Fill it full of hydrogen until it floats. Then see how many bricks you can tie on and it still floats. Have a gun ready to shoot it down in case it is in danger of floating away.

I like this one best. :D

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